KR101821902B1

KR101821902B1 - Chemically strengthened glass

Info

Publication number: KR101821902B1
Application number: KR1020167001477A
Authority: KR
Inventors: 이즈루 가시마; 유스케 후지와라; 기요시 다마이; 유이치 스즈키; 다이스케 고바야시; 요이치 세라; 다쿠 야마다
Original assignee: 아사히 가라스 가부시키가이샤
Priority date: 2013-07-19
Filing date: 2014-07-15
Publication date: 2018-01-24
Also published as: JP2015214481A; CN104736495A; CN104812718B; JPWO2015008764A1; CN106277840B; TWI600631B; JP5776859B2; CN106277840A; DE112014003330T5; CN106316155A; CN104812718A; WO2015008764A1; JP6292171B2; JP6010165B2; JP2015131763A; TW201512136A; KR101838413B1; TWI598311B; TWI620727B; TW201733955A

Abstract

Wherein the hydrogen concentration Y in the region from the outermost surface to the depth X of the glass is in the range of X = 0.1 to 0.4 ( The surface strength F (N) measured by the ball-on-ring test is F > / = 1500 x t ² with respect to the thickness t (mm) of the glass plate, A chemical tempered glass that does not have abrasive scratches on it.
Y = aX + b (I)
[The meaning of each symbol in the formula (I) is as follows.
Y: hydrogen concentration (in terms of H ₂ O, mol / L)
X: depth from the glass surface (mu m)
a: 0.270 to -0.005
b: 0.020 to 0.220]

Description

{CHEMICALLY STRENGTHEN GLASS}

The present invention relates to chemically tempered glass.

2. Description of the Related Art In a flat panel display device such as a digital camera, a mobile phone, or a PDA (Personal Digital Assistants), a thin plate-shaped cover glass is formed on a front surface of a display As shown in Fig. Though the glass has a high theoretical strength, scratches cause a significant decrease in strength. Therefore, a chemical tempered glass in which a compressive stress layer is formed on the glass surface by ion exchange or the like is used for a cover glass which requires strength.

Along with the demand for a lightweight and thinner flat panel display device, it is required to make the cover glass itself thin. Therefore, the cover glass is required to have more strength on both the surface and the end face to satisfy the object.

In order to improve the strength of the chemically tempered glass, conventionally, it is known to perform surface etching treatment after chemical strengthening treatment (Patent Document 1).

Here, with respect to the strength of the glass, it is known that the strength of the glass is lowered by the presence of hydrogen (moisture) in the glass (Non-Patent Documents 1 and 2).

Japanese Patent Publication No. 2013-516387

SITO et al., "Crack Blunting of High-Silica Glass", Journal of the American Ceramic Society, Vol. 65, No. 8, (1982), 368-371 Won-Taek Han et al., "Effect of residual water in silica glass on static fatigue ", Journal of Non-Crystalline Solids, 127, (1991) 97-104

The inventors of the present invention have found that the strength of glass after chemical strengthening may be lowered. The main reason for this is that chemical imperfections are generated by invasion of moisture in the atmosphere into the surface layer of the glass. It has also been found that this phenomenon occurs not only by chemical strengthening but also by a temperature elevation process in the glass manufacturing process.

As a method for removing water from the surface layer of glass, it is considered that the layer containing moisture is shaved off by, for example, polishing the glass surface after chemical strengthening, or immersing it in hydrofluoric acid or the like to perform etching treatment. However, since the glass surface is scratched by polishing, the strength may be lowered. Further, in the case where there is a latent scratch on the glass surface, in the etching treatment using hydrofluoric acid or the like, latent scratches are enlarged, and there is a possibility that appearance defects due to pits are caused. In addition, FOSHAN requires careful handling in terms of safety.

It is an object of the present invention to provide a chemically tempered glass which effectively suppresses a decrease in the strength of glass even when chemical strengthening is performed.

The present inventors have found that when the hydrogen concentration profile in the surface layer of the chemically tempered glass is set within a specific range and the surface roughness (Ra) is a specific value or more, even if the glass surface after chemical strengthening is not polished or subjected to etching treatment using hydrofluoric acid And the reliability of the surface strength is improved, thereby completing the present invention.

That is, the present invention is as follows.

<1>

A chemical tempered glass having a compressive stress layer formed by ion exchange on the surface layer,

A surface roughness (Ra) of 0.20 nm or more,

The hydrogen concentration Y in the region of depth X from the outermost surface of the glass satisfies the following relational expression (I) at X = 0.1 to 0.4 (占 퐉)

And a face strength measured under the conditions tested for by the ring F (N) is F≥1500 × t ² with respect to the plate thickness t (㎜) of the glass sheet, - the ball-on

Also, chemically tempered glass that does not have abrasive scratches on its surface.

Y = aX + b (I)

[The meaning of each symbol in the formula (I) is as follows.

Y: hydrogen concentration (in terms of H ₂ O, mol / L)

X: depth from the glass surface (mu m)

a: -0.270 to -0.005

b: 0.020 to 0.220]

Ball-on-Ring Test Conditions:

A glass plate having a thickness t (mm) was placed on a stainless ring having a diameter of 30 mm and a contact portion having a rounded shape with a radius of curvature of 2.5 mm, and a steel sphere having a diameter of 10 mm was brought into contact with the glass plate. The fracture load (unit N) at the center of the ring under static loading conditions when the glass is broken is called the BOR surface strength, and the measured average value of the BOR surface strength at 20 times is called the surface strength F. However, if the fracture origin of the glass is separated by 2 mm or more from the load point of the sphere, it is excluded from the data for the average value calculation.

&Lt; 2 &

The chemically tempered glass according to the above < 1 >, wherein the glass is aluminosilicate glass, aluminoborosilicate glass or soda lime glass.

According to the chemically tempered glass of the present invention, by setting the hydrogen concentration profile in the glass surface layer to a specific range and by setting the surface roughness (Ra) to a specific value or more, the surface strength of the glass The reliability of the surface strength can be improved.

1 is a schematic diagram for explaining a method of a ball-on-ring test.
Fig. 2 is a schematic view showing a manufacturing process of the chemically tempered glass according to the present invention.
3 is a graph plotting the hydrogen concentration profile of the surface layer of each chemically tempered glass obtained in Examples 1 and 2. Fig.
4 is a graph plotting the hydrogen concentration profile of the surface layer of each chemically tempered glass obtained in Example 3 and Example 4. Fig.
5 is a graph plotting hydrogen concentration profiles of the surface layer of each chemically tempered glass obtained in Comparative Example 1, Comparative Example 2, and Comparative Example 3. Fig.
6 is an explanatory diagram for deriving the relational expression (I) from the graph plotting the hydrogen concentration profile of the surface layer of the chemically tempered glass obtained in Example 1. Fig.
7 is an explanatory diagram for deriving the relational expression (I) from the graph plotting the hydrogen concentration profile of the surface layer of the chemically tempered glass obtained in Comparative Example 1. FIG.
Fig. 8 is a quadrant plot of the BOR surface strength evaluation of each chemically tempered glass obtained in Example 1 and Comparative Example 1. Fig.
9 is an AFM image of the surface of the chemically tempered glass of Reference Example 1. Fig. The scan area is 5 占 5 占 퐉 ² .
10 is an AFM image of the chemically tempered glass surface of Example 1. Fig. The scan area is 5 占 5 占 퐉 ² .
Fig. 11 is a quadrant plot of the BOR surface strength evaluation of each chemically tempered glass obtained in Example 3 and Reference Example 2. Fig.
12 is a graph plotting the hydrogen concentration profile of the surface layer of each chemically tempered glass obtained in Example 3 and Reference Example 2. Fig.
13 is an AFM image of a glass surface having a surface polishing scratch.
14 is an AFM image of a glass surface having no surface polishing scratches.

Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following embodiments, and can be arbitrarily modified without departing from the gist of the present invention.

In the present specification, "mass%" and "weight%", "mass ppm" and "ppm by weight" are respectively synonymous. In the case of simply describing "ppm", it indicates "ppm by weight".

The chemically tempered glass according to the present invention is a chemically tempered glass having a compressive stress layer formed by ion exchange on the surface layer and is characterized in that the concentration of hydrogen in a certain depth region from the outermost surface of the glass satisfies the following relational expression (I) And does not have abrasive scratches on the glass surface.

The compressive stress layer is a high-density layer formed by ion-exchanging Na ions on the glass surface and K ions in the molten salt by bringing the glass as a raw material into contact with an inorganic salt such as potassium nitrate.

In the chemically tempered glass of the present invention, the hydrogen concentration profile in the glass surface layer is within a specific range. Concretely, the hydrogen concentration Y in the region of the depth X from the outermost surface of the glass satisfies the following relational expression (I) at X = 0.1 to 0.4 (mu m).

Y = aX + b (I)

[The meaning of each symbol in the formula (I) is as follows.

Y: hydrogen concentration (in terms of H ₂ O, mol / L)

X: depth (占 퐉) from the outermost surface of the glass

a: -0.270 to -0.005

b: 0.020 to 0.220]

With respect to the surface strength of glass, it is known that the surface strength of glass is lowered by the presence of hydrogen (moisture) in the glass. However, the present inventors have found that the surface strength after the chemical strengthening treatment is lowered, This is because chemical defects are generated by the penetration of water into the glass. It has also been found that this phenomenon occurs not only in the chemical strengthening but also in the glass manufacturing process through the temperature raising process.

When the concentration of hydrogen in the glass is high, hydrogen enters the bonding network of Si-O-Si of the glass in the form of Si-OH, and the bonding of Si-O-Si is broken. If the concentration of hydrogen in the glass is high, portions where Si-O-Si bonds are broken are likely to be formed, and chemical defects are likely to be generated, and the surface strength is considered to be lowered.

The above-mentioned relational expression (I) is established in the region of depth X = 0.1 to 0.4 μm from the outermost surface. The thickness of the compressive stress layer formed by ion exchange depends on the degree of chemical strengthening, but is formed in the range of 5 to 50 mu m. The penetration depth of hydrogen into the glass depends on the diffusion coefficient, the temperature and the time, and the penetration amount of hydrogen influences the moisture amount in the atmosphere. The hydrogen concentration after the chemical strengthening is gradually lowered over the deep portion (bulk) where the outermost surface is the highest and the compressive stress layer is not formed. The relationship (I) defines the degraded state. However, at the outermost surface (X = 0 占 퐉), there is a possibility that the water concentration changes due to the aging deterioration. To 0.4 mu m).

In the formula (I), a is a slope that defines a state of decrease in hydrogen concentration. The range of a is -0.270 to -0.005, preferably -0.240 to -0.030, and more preferably -0.210 to -0.050.

In the formula (I), b corresponds to the hydrogen concentration at the outermost surface (X = 0 占 퐉). The range of b is 0.020 to 0.220, preferably 0.020 to 0.215, more preferably 0.030 to 0.210, and still more preferably 0.040 to 0.200.

Generally, it is considered that the decrease in the surface strength of glass is caused by extension of microcracks present on the glass surface due to mechanical pressure from the outside. According to Non-Patent Document 2, it is considered that the more the Si-OH-rich state of the glass structure at the tip of the crack is, the easier the crack is likely to expand. Assuming that the tip of the crack is exposed in the atmosphere, it is presumed that the Si-OH amount at the tip of the crack shows a positive correlation with the hydrogen concentration at the outermost surface of the glass. Therefore, b, which corresponds to the hydrogen concentration on the outermost surface, is preferably in a range as low as the above.

As shown in Figs. 3 to 5, no significant difference was observed in the penetration depth of hydrogen for the glass subjected to the chemical strengthening process. The depth of penetration of hydrogen is likely to change depending on the chemical strengthening process conditions. However, if it is assumed that it is unchanged, the value of b corresponding to the concentration of hydrogen on the outermost surface and a corresponding to the gradient . Therefore, a is preferably in a range as high as the above.

As described above, in the present invention, not only the hydrogen concentration itself of the surface layer itself is defined, but the hydrogen concentration of the surface layer and the degraded state thereof are specified in a specific range, It can be done.

[Method of measuring hydrogen concentration profile]

Here, the hydrogen concentration profile (H ₂ O concentration, mol / L) of the glass is a profile measured under the following analysis conditions.

Secondary ion mass spectrometry (SIMS) was used to measure the hydrogen concentration profile of the glass substrate. When obtaining a quantitative hydrogen concentration profile in SIMS, a standard sample of hydrogen concentration base is required. A method of producing a standard sample and a method of quantifying the hydrogen concentration will be described below.

1) Cut out a part of the glass substrate to be measured.

2) An area of 50 mu m or more from the surface of the cut glass substrate is removed by polishing or chemical etching. The removal process is performed on both sides. That is, the thickness of removal on both surfaces is 100 mu m or more. This removed glass substrate is referred to as a standard sample.

Calculate the IR), the carried out, the absorption height of the absorbance peak height of the top of the near IR spectrum 3550㎝ ^-1 A ₃₅₅₀ and A ₄₀₀₀ 4000㎝ ^-1 (baseline): 3), infrared spectroscopy (Infrared spectroscopy with respect to a standard sample .

4) The plate thickness d (㎝) of the standard sample is measured using a plate thickness meter such as a micrometer.

5) With reference to Document A, the infrared absorption coefficient ε _pract (L / (mol · cm)) of H ₂ O of glass is 75, and the hydrogen concentration (in terms of H ₂ O, mol / L).

The hydrogen concentration of the standard sample = (A ₃₅₅₀ -A ₄₀₀₀ ) / (? _Pract · d) ... Expression II

A) S.Ilievski et al., Glastech. Ber. Glass Sci. Technol., 73 (2000) 39.

Conveying a standard sample of known concentration of hydrogen obtained by the glass substrate and the method of the object to be measured at the same time into the SIMS apparatus, and subjected to measurement in order, ¹ ^H-acquires the depth direction profile of the intensity of ^the-30 and Si. Then, ¹ ^H-Si ³⁰ from the profile ^- Except for profile, ¹ H ^- / ³⁰ Si ^- is obtained in a depth direction profile of the intensity ratio. The average ¹ H ^- / ³⁰ Si ^- intensity ratio in the region from the depth of 1 탆 to 2 탆 is calculated from the depth direction profile of the ¹ H ^- / ³⁰ Si ^- intensity ratio of the standard sample, Is created to pass through the origin (the calibration curve at the first level of the standard sample). Using this calibration curve, the ¹ H ^- / ³⁰ Si ^- intensity ratio of the longitudinal axis of the profile of the glass substrate to be measured is converted to the hydrogen concentration. Thereby, the hydrogen concentration profile of the glass substrate to be measured is obtained. The measurement conditions of SIMS and IR are as follows.

[Measurement conditions of SIMS]

Device: ADPT1010 manufactured by ULPAK PASIER

Primary ion species: Cs ⁺

Acceleration voltage of primary ion: 5 kV

Current value of primary ion: 500 nA

Incident angle of primary ion: 60 ° with respect to the normal of the sample surface

Raster size of primary ion: 300 × 300 μm ²

Polarity of secondary ion: minus

Secondary ion detection area: 60 占 60 占 퐉 ² (4% of raster size of primary ion)

ESA Input Lens: 0

Use of neutralization gun: Yes

Method of converting the horizontal axis from the sputter time to the depth: The depth of the analytical crater is measured by a stylus type surface profilometer (Dektak 150 manufactured by Veeco) to obtain the sputter rate of the primary ion. Using this sputter rate, the axis of abscissas is converted from sputter time to depth.

¹ H ^- Field Axis Potential at Detection: There is a possibility that the optimum value changes for each device. Set the value with care that the background is cut sufficiently.

[Measurement conditions of IR]

Apparatus: Nic-plan / Nicolet 6700 from Thermo Fisher Scientific

Resolution: 4 cm ^-1

Total: 16

Detector: TGS detector

In order to derive the relational expression (I) from the hydrogen concentration profile (H ₂ O concentration, mol / L) of the glass measured by the above analysis conditions, the following procedure is used. As shown in Figs. 6 and 7, a linear approximation is performed on the hydrogen concentration profile in the depth region of 0.1 to 0.4 mu m. The formula of the obtained approximate straight line is referred to as Relation (I).

Examples of means for controlling a and b include, for example, changing the flux concentration, sodium concentration, temperature, time, etc. in the chemical strengthening process.

The chemical tempered glass according to the present invention preferably has an average hydrogen concentration c of 0.070 to 0.150 mol / L in the region of the root surface (depth X from the outermost surface = 0.1 to 0.4 mu m). If the average hydrogen concentration is within this range, it is considered that not only the high surface strength but also the reliability of the surface strength is improved. The average hydrogen concentration c can be obtained from the hydrogen concentration profile described above.

(Surface polishing scratches)

The chemical tempered glass according to the present invention has no abrasive scratches on its surface. In the present invention, the term "polishing" refers to smoothing by abrading the glass surface using abrasive grains. The presence or absence of abrasive scratches can be judged by observing the surface by AFM (Atomic Force Microscope). In the region of 10 占 퐉 占 5 占 퐉, two or more scratches having a length of 5 占 퐉 or more and a width of 0.1 占 퐉 or more exist It can be said that there is no polishing scratch on the surface. Fig. 13 shows a state in which a surface polishing scratch is present, and Fig. 14 shows a state in which no surface scratch scratch is present.

(Glass surface strength)

The surface strength of the chemically tempered glass of the present invention can be evaluated by a ball-on-ring test.

(Ball-on-ring test)

The chemically tempered glass of the present invention is obtained by arranging a glass plate on a ring including a stainless steel having a diameter of 30 mm and a contact portion having a rounded shape with a radius of curvature of 2.5 mm and contacting the glass plate with a sphere including a steel having a diameter of 10 mm , The spheres are evaluated by the BOR surface strength F (N) measured by the Ball-on-Ring (BOR) test, which is loaded at the center of the ring under static loading conditions.

Chemical tempered glass of the invention, and F≥1500 × t ^2, t × F≥1800 more preferably ² to [wherein, F is a ball-and BOR surface strength (N) was measured by the ring test -one , and t is the thickness (mm) of the glass substrate. Since the BOR surface strength F (N) is within this range, even a thin sheet exhibits excellent surface strength.

Fig. 1 shows a schematic diagram for explaining the ball-on-ring test used in the present invention. In the Ball-on-Ring (BOR) test, a glass jig 2 (quenching steel, 10 mm in diameter, mirror-finished surface) made of SUS304, (1) is pressed to measure the surface strength of the glass plate (1).

1, a glass plate 1 as a sample is horizontally provided on a support jig 3 made of SUS304 (30 mm in diameter, R2.5 mm in contact portion, quenched steel, mirror finish). Above the glass plate 1, a pressing jig 2 for pressing the glass plate 1 is provided.

In the present embodiment, the central region of the glass plate 1 is pressed from above the glass plate 1 obtained after the examples and the comparative examples. The test conditions are as follows.

The descending speed of the pressing jig 2: 1.0 (mm / min)

At this time, the fracture load (unit N) when the glass is broken is referred to as BOR surface strength, and the average value of 20 measurements is referred to as surface strength F. However, if the fracture origin of the glass plate is separated by 2 mm or more from the load point of the sphere, it is excluded from the data for average value calculation.

The chemical tempered glass of the present invention has high surface strength in addition to the above-mentioned high surface strength, and also has high reliability of surface strength. As can be seen in the following examples and the quadrant plots of the BOR surface strength evaluation of each chemically tempered glass, the chemical tempered glass of the present invention shows less variation in surface strength. The reason for this is not clear, but it is presumed that the hydrogen (moisture) concentration near the glass surface layer is a little high.

(Surface roughness)

The chemical tempered glass of the present invention has a surface roughness (Ra) of 0.20 nm or more. When the surface roughness is equal to or larger than the above-mentioned numerical value, chemical strengthening glass having a high surface strength can be obtained. It is presumed that the glass surface has a certain level of surface roughness, whereby the stress concentration is suppressed and the surface strength is increased.

The surface roughness can be measured by, for example, observing the surface of the AFM with a measurement range of 1 탆 1 탆.

In addition, the surface roughness of the conventional untreated chemically tempered glass plate is less than 0.20 nm.

[Measurement conditions of AFM]

Device: manufactured by Bruker NanoscopeV + MultiMode 8 or Dimension ICON

Mode: ScanAsyst mode

Probe: RTESPA (spring constant: 40 N / m)

Samples / Line: 256

Lines: 256

Scan Rate: 1㎐

Measurement field of view: 1 x 1 탆 ² (aimed at no contamination)

&Lt; Production method of chemically tempered glass >

One mode of the method for producing the chemically tempered glass according to the present invention is described below, but the present invention is not limited thereto.

(Glass composition)

The glass used in the present invention may contain sodium and may have various compositions as long as it has a composition capable of being reinforced by molding and chemical strengthening treatment. Specific examples thereof include aluminosilicate glass, soda lime glass, borosilicate glass, lead glass, alkali barium glass, aluminoborosilicate glass, and the like.

The production method of the glass is not particularly limited, and a desired glass raw material is put into a continuous melting furnace, and the glass raw material is preferably heated and melted at 1500 to 1600 占 폚, refined, Molding, and slowly cooling.

In addition, various methods can be adopted for forming the glass. For example, various molding methods such as a down-draw method (for example, an overflow down-draw method, a slot-down method and a read-draw method), a float method, a roll-out method, and a press method can be employed.

The thickness of the glass is not particularly limited, but is preferably 5 mm or less, and more preferably 3 mm or less in order to effectively perform the chemical strengthening treatment.

The shape of the glass used in the present invention is not particularly limited. For example, glass having various shapes such as a plate shape having a uniform plate thickness, a shape having a curved surface on at least one of the surface and the back surface, and a three-dimensional shape having a bent portion or the like can be adopted.

The composition of the chemically tempered glass of the present invention is not particularly limited, and examples of the composition of the following glasses are mentioned.

(i) expressed in mol%, SiO ₂ in an amount of 50 to 80%, Al ₂ O ₃ 2 to 25%, Li ₂ O 0 to 10%, Na ₂ O 0 to 18%, K ₂ O 0 to 10%, MgO 0 to 15%, CaO 0 to 5% and ZrO ₂ to 0 &Lt; / RTI > to 5%

(ii) is a composition represented by mol%, 50 to 74% of SiO _2, Al 1 to 10% by the ₂ O _3, 6 to 14% of Na ₂ O, 3 to 11% of K ₂ O, the MgO 2 To 15% of CaO, 0 to 6% of CaO and 0 to 5% of ZrO ₂ , the total content of SiO ₂ and Al ₂ O ₃ is 75% or less, the total content of Na ₂ O and K ₂ O is 12 To 25%, a total content of MgO and CaO of 7 to 15%

(iii) is a composition represented by mol%, SiO ₂ of 68 to 80%, Al ₂ O ₃ 4 to 10%, an Na ₂ O 5 to 15%, the K ₂ O 0 to 1%, the MgO 4 To 15% of ZrO ₂ and 0 to 1% of ZrO ₂

(iv) is a composition represented by mol%, SiO ₂ of 67 to 75%, Al ₂ O ₃ 0 to 4% Na ₂ O 7 to 15%, the K ₂ O 1 to 9%, the MgO 6 To 14% and ZrO _{2 in an amount} of 0 to 1.5%, the total content of SiO ₂ and Al ₂ O ₃ is 71 to 75%, the total content of Na ₂ O and K ₂ O is 12 to 20% The glass having a content of less than 1%

The chemically tempered glass according to the present invention has on the glass surface an ion-exchanged compressive stress layer. In the ion exchange method, the surface of the glass is ion-exchanged to form a surface layer in which compressive stress remains. Concretely, alkali metal ions (typically, Li ion, Na ion) having a small ionic radius on the surface of the glass plate are ion-exchanged with an alkali ion of larger ionic radius (typically, Li Na ion or K ion for the ion, and K ion for the Na ion). Thereby, a compressive stress remains on the surface of the glass, and the surface strength of the glass is improved.

In the production process of the present invention, the chemical strengthening is carried out by bringing the glass into contact with an inorganic salt containing potassium nitrate (KNO ₃ ). Whereby Na ions on the glass surface and K ions in the inorganic salt are ion-exchanged to form a high-density compressive stress layer. As a method for bringing the glass into contact with the inorganic salt, it is possible to apply a paste-like salt, a method of spraying an aqueous solution of a salt onto a glass, a method of immersing a glass in a salt bath of a molten salt heated to a melting point or higher, , A method of immersing in a molten salt is preferred.

As the inorganic salt, it is preferable that the inorganic salt has a melting point of not higher than the strain point (usually 500 to 600 ° C) of the glass to be chemically strengthened, and in the present invention, a molten salt containing potassium nitrate (melting point 330 ° C) is preferable. It is preferable that it is molten at a point below the strain point of the glass by containing potassium nitrate and that handling in the use temperature range is facilitated. The content of potassium nitrate in the inorganic salt is preferably 50% by mass or more.

Inorganic salts may also be selected from the group consisting of K ₂ CO ₃ , Na ₂ CO ₃ , KHCO ₃ , NaHCO ₃ , K ₃ PO ₄ , Na ₃ PO ₄ , K ₂ SO ₄ , Na ₂ SO ₄ , KOH and NaOH It is preferable to contain at least one kind of salt, more preferably at least one kind of salt selected from the group consisting of K ₂ CO ₃ , Na ₂ CO ₃ , KHCO ₃ and NaHCO ₃ .

The salt (hereinafter also referred to as " flux ") has a property of cutting a network of glass represented by Si-O-Si bond. The temperature at which the chemical strengthening treatment is carried out is as high as several hundreds of degrees Celsius, so that the covalent bond between the Si-O bonds of the glass under such temperature is suitably cleaved, and the low density treatment described later tends to proceed.

The extent to which the covalent bond is cleaved varies depending on the chemical composition of the glass, the type of salt (flux) used, the temperature at which the chemical strengthening treatment is carried out, and the chemical strengthening treatment conditions such as time. However, , It is considered that it is preferable to select the condition of the degree to which one or two bonds are broken.

For example, in the case where K ₂ CO ₃ is used as a flux, when the content of the flux in the inorganic salt is 0.1 mol% or more and the chemical strengthening treatment temperature is 350 to 500 ° C., the chemical strengthening treatment time is 1 min To 10 hours, more preferably 5 minutes to 8 hours, still more preferably 10 minutes to 4 hours.

The addition amount of the flux is preferably 0.1 mol% or more, more preferably 1 mol% or more, and particularly preferably 2 mol% or more, from the viewpoint of surface hydrogen concentration control. Further, from the viewpoint of productivity, the saturation solubility of each salt is preferably at most. If it is added in excess, there is a risk of corrosion of the glass. For example, when K ₂ CO ₃ is used as a flux, it is preferably not more than 24 mol%, more preferably not more than 12 mol%, particularly preferably not more than 8 mol%.

In addition to potassium nitrate and flux, inorganic salts may contain other chemical species within the range that does not impair the effect of the present invention. For example, alkali salts such as sodium chloride, potassium chloride, sodium borate and potassium borate and alkali borate salts . These may be added alone or in combination of a plurality of species.

Hereinafter, the production method of the present invention will be described taking, as an example, a form in which chemical strengthening is performed by immersing the glass in a molten salt.

(Production of molten salt 1)

The molten salt can be produced by the process shown below.

Step 1a: Preparation of potassium nitrate molten salt

Step 2a: Addition of flux to molten salt of potassium nitrate

(Process 1 - Preparation of molten salt of potassium nitrate-)

In Step 1a, potassium nitrate is charged into a vessel, and the mixture is heated to a temperature not lower than the melting point to melt, thereby preparing a molten salt. Melting is carried out at a temperature within the range of the melting point (330 캜) and boiling point (500 캜) of potassium nitrate. In particular, it is more preferable to set the melting temperature to 350 to 470 DEG C in view of the balance between the surface compressive stress CS and the compressive stress layer depth DOL which can be imparted to the glass, and the strengthening time.

As a container for melting potassium nitrate, metal, quartz, ceramics, or the like can be used. Among them, a metal material is preferable from the viewpoint of durability, and a stainless steel (SUS) material is preferable from the viewpoint of corrosion resistance.

(Step 2 - Addition of Flux to Potassium Nitrate Molten Salt-)

In step 2a, the above-mentioned flux is added to the molten salt of potassium nitrite prepared in step 1a, and the mixture is mixed by a stirring blade or the like while keeping the temperature within a certain range. When a plurality of fluxes are used in combination, the order of addition is not limited and may be added at the same time.

The temperature is preferably at least the melting point of potassium nitrate, that is, 330 DEG C or more, more preferably 350 to 500 DEG C. The stirring time is preferably 1 minute to 10 hours, more preferably 10 minutes to 2 hours.

(Preparation 2 of molten salt)

In Production 1 of the molten salt, a method of adding a flux after the preparation of a molten salt of potassium nitrate is exemplified, but the molten salt can also be produced by the following process.

Step 1b: Mixing of potassium nitrate with flux

Step 2b: Melting of mixed salt of potassium nitrate and flux

(Step 1b-mixing of potassium nitrate and flux)

In Step 1b, potassium nitrate and a flux are put into a vessel and mixed by a stirring blade or the like. When a plurality of fluxes are used in combination, the order of addition is not limited and may be added at the same time. The same container as used in the above step 1a may be used.

(Step 2b-Melting of mixed salt of potassium nitrate and flux)

In Step 2b, the mixed salt obtained in Step 1b is heated and melted. Melting is carried out at a temperature within the range of the melting point (330 캜) and boiling point (500 캜) of potassium nitrate. In particular, it is more preferable to set the melting temperature to 350 to 470 DEG C in view of the balance between the surface compressive stress CS and the compressive stress layer depth DOL which can be imparted to the glass, and the strengthening time. The stirring time is preferably 1 minute to 10 hours, more preferably 10 minutes to 2 hours.

In the case where a precipitate is generated by the addition of a flux in the molten salt obtained through the steps 1a and 2a or the steps 1b and 2b, the precipitate is precipitated on the bottom of the container before chemical strengthening treatment of the glass I will stay until I do. This precipitate includes a flux exceeding the saturation solubility or a salt in which the cation of the flux is exchanged in the molten salt.

The molten salt used in the production method of the present invention has an Na concentration of preferably at least 500 ppm by weight, more preferably at least 1000 ppm by weight. The Na concentration in the molten salt is at least 500 ppm by weight because the low-density layer becomes easy to be deepened by an acid treatment step described later. The upper limit of the Na concentration is not particularly limited and may be allowed until a desired surface compressive stress (CS) is obtained.

The molten salt subjected to the chemical strengthening treatment at least once contains sodium dissolved from the glass. Therefore, if the Na concentration is already in the above range, the sodium derived from the glass may be used as the Na source as it is, or when the Na concentration is not satisfied or when the chemical strengthening unused molten salt is used, Can be adjusted by adding a sodium salt.

As described above, the molten salt can be prepared by the steps 1a and 2a, or the steps 1b and 2b.

(Chemical strengthening)

Then, chemical strengthening treatment is performed using the prepared molten salt. The chemical strengthening treatment is performed by immersing the glass in a molten salt and replacing metal ions (Na ions) in the glass with metal ions (K ions) having a large ion radius in the molten salt. By this ion exchange, the composition of the glass surface is changed, and the compressive stress layer 20 in which the glass surface is densified can be formed (Fig. 2 (a) to (b)). The glass can be strengthened in that the compressive stress is generated by the high density of the glass surface.

Actually, the density of the chemically tempered glass is gradually increased from the outer edge of the intermediate layer 30 (bulk) existing in the center of the glass toward the surface of the compressive stress layer, so that the density is increased between the intermediate layer and the compressive stress layer There is no clear boundary that changes rapidly. The term " intermediate layer " refers to a layer that exists in the glass center portion and is sandwiched by the compressive stress layer. Unlike the compressive stress layer, this intermediate layer is a layer which is not ion-exchanged.

Specifically, the chemical strengthening treatment in the present invention can be carried out by the following Step 3.

Step 3: Chemical strengthening treatment of glass

(Process 3 - Chemical strengthening treatment of glass-)

In Step 3, the glass is preheated, and the molten salt prepared in Steps 1a and 2a or Steps 1b and 2b is adjusted to a temperature at which the chemical strengthening is performed. Subsequently, the preheated glass is immersed in the molten salt for a predetermined period of time, and then the glass is drawn up in the molten salt and allowed to cool. The glass is preferably subjected to shape processing such as cutting, end face machining, and punching machining depending on the application before the chemical strengthening treatment.

The preheating temperature of the glass depends on the temperature at which it is immersed in the molten salt, but it is generally preferably 100 ° C or higher.

The chemical strengthening temperature is preferably not higher than the strain point (usually 500 to 600 ° C) of the tempered glass, and preferably 350 ° C or more in order to obtain a higher compressive stress layer depth.

The immersion time of the glass in the molten salt is preferably from 1 minute to 10 hours, more preferably from 5 minutes to 8 hours, even more preferably from 10 minutes to 4 hours. Within this range, a chemically tempered glass having excellent balance between the surface strength and the depth of the compressive stress layer can be obtained.

In the production method of the present invention, the following steps are performed after chemical strengthening treatment.

Step 4: Cleaning the glass

Step 5: Acid treatment of the glass after step 4

The glass surface further has a low density layer 10 in which the surface layer of the compressive stress layer 20 is modified, specifically a low density layer 10 (see FIGS. 2 (b) to 2 (c)), ]. The low-density layer is formed by letting Na (Na) or K (Na) from the outermost surface of the compressive stress layer enter (substitute) H instead.

Hereinafter, Step 4 and Step 5 will be described in detail.

(Step 4 - Cleaning of glass-)

In Step 4, glass is cleaned using air, ion-exchange water, or the like. Among them, ion-exchange water is preferable. The conditions of the cleaning vary depending on the cleaning liquid used, but in the case of using ion-exchanged water, cleaning at 0 to 100 캜 is preferable in that the deposited salt is completely removed.

(Step 5-Acid treatment-)

In step 5, the glass washed in step 4 is further acid-treated.

The acid treatment of the glass is carried out by immersing the chemically tempered glass in an acidic solution, whereby the Na and / or K on the chemically tempered glass surface can be replaced with H.

The pH of the solution is not particularly limited as long as it is acidic and less than pH 7, and the acid used may be weak acid or strong acid. Specifically, acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, acetic acid, oxalic acid, carbonic acid and citric acid are preferable. These acids may be used alone, or a plurality of acids may be used in combination.

The temperature at which the acid treatment is carried out is preferably carried out at 100 占 폚 or lower though it depends on the type and concentration of the acid used and the time.

The time for carrying out the acid treatment varies depending on the type and concentration of the acid used and the temperature, but is preferably from 10 seconds to 5 hours from the viewpoint of productivity and more preferably from 1 minute to 2 hours.

The concentration of the solution to be subjected to the acid treatment varies depending on the type, time, and temperature of the acid to be used, but is preferably such a concentration that there is less concern about corrosion of the vessel, specifically 0.1 wt% to 20 wt%.

Since the low-density layer is removed by an alkali treatment to be described later, the thicker the low-density layer, the more likely the glass surface is removed. Therefore, the thickness of the low-density layer is preferably 5 nm or more, and more preferably 20 nm or more, from the viewpoint of the removal amount of the glass surface. The thickness of the low density layer can be controlled by the flux concentration, sodium concentration, temperature, time, etc. in the chemical strengthening process.

The density of the low-density layer is preferably lower in comparison with the density of the region (bulk) deeper than the ion-exchanged compressive stress layer, from the viewpoint of glass surface removability.

The thickness of the low-density layer can be obtained from the period (??) measured by X-ray reflectometry (XRR).

The density of the low-density layer can be obtained by the critical angle &thetas; c measured by XRR.

It is also possible to simply check the formation of the low density layer and the thickness of the layer by observing the cross section of the glass with a scanning electron microscope (SEM).

In the production method of the present invention, the following steps are carried out after the acid treatment.

Step 6: Alkali treatment

By the step 6, part or all of the low-density layer 10 formed up to the step 5 can be removed (Fig. 2 (c) to (d)).

Hereinafter, step 6 will be described in detail.

(Step 6 - alkali treatment-)

In step 6, the alkali-treated glass is further subjected to acid treatment in step 5.

The alkali treatment is carried out by immersing the chemically tempered glass in the basic solution, whereby part or all of the low-density layer can be removed.

The pH of the solution is not particularly limited as long as it is basic, and the pH may be more than 7, and a weak base or strong base may be used. Specifically, bases such as sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate and the like are preferable. These bases may be used alone, or a plurality of bases may be used in combination.

The temperature at which the alkali treatment is performed is preferably 0 to 100 占 폚, more preferably 10 to 80 占 폚, and particularly preferably 20 to 60 占 폚, depending on the kind, concentration and time of the base to be used. Such a temperature range is preferable because there is no fear that the glass will corrode.

The time for performing the alkali treatment varies depending on the type and concentration of the base used and the temperature, but is preferably from 10 seconds to 5 hours in terms of productivity and more preferably from 1 minute to 2 hours.

The concentration of the solution to be subjected to the alkali treatment varies depending on the type, time and temperature of the base to be used, but is preferably 0.1 wt% to 20 wt% from the viewpoint of glass surface removability.

By the alkali treatment, part or all of the low-density layer into which H has entered is removed, and the surface layer having the hydrogen concentration profile satisfying the above-mentioned specific relational expression (I) is exposed. Thereby, a chemically tempered glass having improved surface strength can be obtained. In addition, since the low-density layer is removed, scratches existing on the glass surface are also removed at the same time, and this viscosity is considered to contribute to the improvement of the surface strength.

After the completion of the acid treatment step 5 and the alkali treatment step 6 or the alkali treatment step 6, it is preferable to have the same cleaning step as in step 4.

According to the manufacturing method of the present invention, since the safety of the chemical liquid to be handled is high, special facilities are not required. Therefore, a chemically tempered glass with remarkably improved surface strength can be obtained safely and efficiently.

The amount of the low density layer to be removed depends on the conditions of the alkali treatment. 2 (d) shows a state in which the low-density layer 10 is completely removed, but a part of the low-density layer 10 may be removed and a part thereof may remain. From the viewpoint of improving the surface strength, an effect can be obtained without removing all the low-density layers. However, from the viewpoint of stably ensuring the transmittance of the glass, it is preferable to remove all of the low-density layers.

Example

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

Various evaluations in this embodiment were performed by the following analysis method.

(Evaluation of glass: surface stress)

The compressive stress value of the compressive stress layer of the chemically tempered glass of the present invention and the depth of the compressive stress layer are measured using an electron probe micro analyzer (EPMA) or a surface stress meter (e.g., FSM-6000 manufactured by Orihara Seisakusho) . In the examples, the surface compressive stress value (CS, unit: MPa) and the depth of compressive stress layer (DOL, unit: 탆) were measured using a surface stress meter (FSM-6000) manufactured by Orihara Seisakusho Co.,

(Evaluation of glass: removal amount)

The thickness of the removed glass was determined by measuring the weight before and after the chemical liquid treatment using an analytical electronic balance (HR-202i, manufactured by A & D) and calculating the thickness by using the following equation.

(Weight of removed portion per one side) = ((weight before processing) - (weight after processing)) / (specific gravity of glass) / treatment area / 2

At this time, the glass specific gravity was calculated to be 2.48 (g / cm 3).

(Evaluation of glass: surface strength)

Glass surface strength was measured by Ball-on-Ring (BOR) test. Fig. 1 shows a schematic diagram for explaining the ball-on-ring test used in the present invention. The glass plate 1 was pressed using a pressing jig 2 (quenching steel, diameter 10 mm, mirror finish) made of SUS304 in a state where the glass plate 1 was placed horizontally, Respectively.

1, a glass plate 1 as a sample is horizontally provided on a support jig 3 made of SUS304 (30 mm in diameter, curvature R 2.5 mm in contact portion, quenched steel, mirror finish). Above the glass plate 1, a pressing jig 2 for pressing the glass plate 1 is provided.

In the present embodiment, the central region of the glass plate 1 was pressed from above the glass plate 1 obtained after Examples and Comparative Examples. The test conditions are as follows.

The descending speed of the pressing jig 2: 1.0 (mm / min)

At this time, the fracture load (unit N) when the glass was broken was referred to as BOR surface strength, and the average value of 20 measurements was referred to as surface strength F. [ However, if the fracture origin of the glass plate is separated by 2 mm or more from the load point of the corresponding specimen, it is excluded from the data for the average value calculation.

(Evaluation of glass: surface roughness)

The surface roughness of the glass was measured under the following conditions using AFM.

[Measurement conditions of AFM]

Device: manufactured by Bruker NanoscopeV + MultiMode 8 or Dimension ICON

Mode: ScanAsyst mode

Probe: RTESPA (spring constant: 40 N / m)

Samples / Line: 256

Lines: 256

Scan Rate: 1㎐

Measurement field of view: 1 x 1 탆 ² (aimed at no contamination)

(Evaluation of glass: hydrogen concentration)

(I) and an average hydrogen concentration (c value) were derived by measuring the hydrogen concentration profile in accordance with the method described in the above-mentioned method for measuring the hydrogen concentration profile.

&Lt; Example 1 >

(Chemical strengthening process)

9700 g of potassium nitrate, 890 g of potassium carbonate and 400 g of sodium nitrate were added to a cup made of SUS and heated to 450 캜 with a mantle heater to prepare a molten salt of potassium carbonate 6 mol% and sodium 10000 ppm by weight. Aluminosilicate glass A (specific gravity: 2.48) having a size of 50 mm x 50 mm x 0.56 mm was prepared, preheated at 200 to 400 DEG C, immersed in a molten salt at 450 DEG C for 2 hours, To perform chemical strengthening treatment. The resulting chemically tempered glass was washed with water and provided to the next step.

Aluminosilicate Glass A Composition (expressed in mol%): SiO ₂ 64.4%, Al ₂ O ₃ 8.0%, Na ₂ O 12.5%, K ₂ O 4.0%, MgO 10.5%, CaO 0.1%, SrO 0.1%, BaO 0.1 %, ZrO ₂ 0.5%

(Acid treatment process)

13.4 wt% hydrochloric acid (HCl; manufactured by KANTO CHEMICAL Co., Ltd.) was prepared in a beaker, and the temperature was adjusted to 41 째 C using a water bath. The glass obtained in the chemical strengthening step was immersed in the adjusted hydrochloric acid for 180 seconds to carry out the acid treatment, after which it was washed several times with pure water and then dried by air blowing. The thus obtained glass was provided in the next step.

(Alkali treatment step)

A 4.0 wt% aqueous solution of sodium hydroxide was prepared in a beaker, and the temperature was adjusted to 40 캜 using a water bath. The glass obtained in the acid treatment step was immersed in the adjusted aqueous sodium hydroxide solution for 120 seconds to carry out the alkali treatment, and thereafter, the glass was washed several times with pure water and then dried by air blowing.

From the above, the chemically tempered glass of Example 1 was obtained.

&Lt; Example 2 >

The procedure of Example 1 was repeated except that aluminosilicate glass A having the plate thickness shown in Table 1 was used and the molten salt temperature and the ion exchange time were set to 430 ° C. and 40 minutes respectively and the aqueous hydrochloric acid solution and sodium hydroxide aqueous solution adjusted using a glass- Chemical-tempered glass was produced in the same manner as in Example 1 except that the glass was sprayed with a shower in 277 seconds each, and acid treatment and alkali treatment were carried out.

&Lt; Example 3 >

(Specific gravity: 2.41) having the following composition was used in place of the aluminosilicate glass A, and that the amount of nitric acid (HNO ₃ : Manufactured by Kagaku Kogyo Co., Ltd.) was prepared in a resin tank, the temperature was adjusted at 41 ° C using a fluorine resin-coated heater (KKS14A; manufactured by HAKODO), and the substrate was immersed in the adjusted nitric acid for 120 seconds, Otherwise, the chemical tempered glass was produced in the same manner as in Example 1.

Aluminosilicate Glass B Composition (expressed in mol%): SiO ₂ 68%, Al ₂ O ₃ 10%, Na ₂ O 14%, MgO 8%

A chemical tempered glass was produced in the same manner as in Example 3 except that aluminosilicate glass A was replaced with aluminoborosilicate glass (specific gravity: 2.38) of 50 mm x 50 mm x 0.70 mm in the following composition in place of aluminosilicate glass A.

Alumino borosilicate glass composition (expressed in mol%): SiO ₂ 67%, B ₂ O ₃ 4%, Al ₂ O ₃ 13%, Na ₂ O 14%, K ₂ O <1%, MgO ₂ % One%

&Lt; Comparative Example 1 &

A chemical tempered glass was produced in the same manner as in Example 1 except that the amount of sodium in the molten salt in the chemical strengthening process was the value shown in Table 1, the amount of potassium carbonate added was 0 g, and the acid treatment step and the alkali treatment step were not carried out .

&Lt; Comparative Example 2 &

A chemical tempered glass was produced in the same manner as in Example 2 except that the amount of sodium in the molten salt in the chemical strengthening step was the value shown in Table 1, the amount of potassium carbonate added was 0 g, and the acid treatment step and the alkali treatment step were not carried out .

&Lt; Comparative Example 3 &

A chemical tempered glass was produced in the same manner as in Example 3 except that the amount of sodium in the molten salt in the chemical strengthening step was the value shown in Table 1, the amount of potassium carbonate added was 0 g, and the acid treatment step and the alkali treatment step were not carried out .

Various evaluations were performed on the thus obtained chemical tempered glass. The results are shown in Table 1.

3 to 5 are graphs showing the hydrogen concentration profiles of the surface layer of each chemically tempered glass obtained in Examples 1 to 4 and Comparative Examples 1 to 3.

Fig. 8 shows a damping plot of the BOR surface strength evaluation of each of the chemically tempered glass obtained in Example 1 and Comparative Example 1. Fig. Fig. 8 shows a wobble plot of the BOR surface strength evaluation result of an aluminosilicate glass plate sample having a plate thickness of 0.56 mm. The horizontal axis of the graph represents the logarithm of the fracture load? (N) ln (?), While the vertical axis represents the cumulative fracture probability Percentage P (%) of the samples in each of the two groups.

From the results shown in Table 1, in Examples 1 to 4 having a surface roughness Ra of 0.20 nm or more and satisfying the relational expression (I), the surface strength was significantly improved as compared with Comparative Examples 1 to 3.

From the results shown in Fig. 8, the average breaking load was 827N in Example 1 and 455N in Comparative Example 1. The 10% fracture load (B10) was 793N in Example 1, 318N in Comparative Example 1, and 1 N% fracture load B1 was 750N in Example 1 and 200N in Comparative Example 1. From this result, it can be understood that the low strength article is not generated in Embodiment 1, and the reliability against the surface strength is greatly improved.

(Reference Example 1)

Cerium oxide having an average particle size of 1.2 占 퐉 was dispersed in water to prepare a slurry having a specific gravity of 0.9 and an aluminosilicate glass B similar to that of Example 3 was polished at a polishing pressure of 10 ㎪ and a polishing pad (nonwoven fabric type) Respectively. The glass obtained in the polishing step was chemically reinforced by using a molten salt similar to that of Comparative Example 3 at a chemical strengthening temperature of 450 캜 and a chemical strengthening treatment time of 2 hours. Table 1 shows the results of various evaluations. An image of this glass surface observed by AFM is shown in Fig. The surface roughness (Ra) measured by AFM measurement was 0.40 nm.

Fig. 10 shows an image of the surface of the chemically tempered glass produced in Example 1. Fig. The surface roughness (Ra) measured by AFM measurement was 0.33 nm.

(Reference Example 2)

Aluminosilicate glass B similar to that in Example 3 was chemically reinforced by using a molten salt similar to that of Comparative Example 3 at a chemical strengthening treatment temperature of 450 ° C and a chemical strengthening treatment time of 2 hours. The glass after the chemical strengthening was immersed in a solution at 25 캜 containing 1.0 wt% of hydrofluoric acid and 18.5 wt% of hydrochloric acid for 60 seconds to etch 1.06 탆 on one side.

Fig. 11 shows a damping plot of the BOR surface strength evaluation of each of the chemically tempered glass obtained in Referential Example 2 and Example 3. Fig. The average breaking load was 1362 N in Example 3 and 1266 N in Reference Example 2. [ The 10% fracture load (B10) was 1339N in Example 3, 1098N in Reference Example 2, and 1304N in Example 3, while the 1% fracture load (B1) was 904N in Reference Example 2. From this result, it can be seen that the third embodiment does not generate a low strength article, and the reliability of the surface strength is greatly improved.

12 shows the hydrogen concentration profile of the surface layer of each chemically tempered glass obtained in Referential Example 2 and Example 3. Fig. The hydrogen concentration in the surface layer was higher in Example 3 than in Reference Example 2. The average hydrogen concentration c in the region of the muscle surface (depth X from the outermost surface = 0.1 to 0.4 占 퐉) in Reference Example 2 was lower than the average hydrogen concentration c in Examples 1 to 4. From this, it is presumed that the reason is not clear, but the improvement in reliability against the surface strength is due to the fact that the hydrogen (moisture) concentration in the vicinity of the glass surface layer is slightly higher.

Although the present invention has been described in detail with reference to specific embodiments, it is apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on Japanese Patent Application No. 2013-151116 filed on July 19, 2013, the contents of which are incorporated herein by reference.

According to the present invention, chemically tempered glass with greatly improved surface strength can be obtained safely and at low cost. The chemical tempered glass according to the present invention can be used in a cover glass for a display such as a cellular phone, a digital camera, or a touch panel display.

10: Low density layer
20: Compressive stress layer
30: middle layer

Claims

A chemical tempered glass having a compressive stress layer formed by ion exchange on the surface layer,
A surface roughness (Ra) of 0.20 nm or more,
The hydrogen concentration Y in the region of depth X from the outermost surface of the glass satisfies the following relational expression (I) at X = 0.1 to 0.4 (占 퐉)
And a face strength measured under the conditions tested for by the ring F (N) is F≥1500 × t ² with respect to the plate thickness t (㎜) of the glass sheet, - the ball-on
Further, a chemically tempered glass in which no scratches of 5 占 퐉 or more and 0.1 占 퐉 or more in width are present in the 10 占 퐉 占 5 占 퐉 area of the surface.
Y = aX + b (I)
[The meaning of each symbol in the formula (I) is as follows.
Y: hydrogen concentration (in terms of H ₂ O, mol / L)
X: depth from the glass surface (mu m)
a: -0.270 to -0.005
b: 0.020 to 0.220]
Ball-on-Ring Test Conditions:
A glass plate having a thickness t (mm) was placed on a stainless ring having a diameter of 30 mm and a contact portion having a rounded shape with a radius of curvature of 2.5 mm, and a steel sphere having a diameter of 10 mm was brought into contact with the glass plate. The fracture load (unit N) at the center of the ring under static loading conditions when the glass is broken is called the BOR surface strength, and the measured average value of the BOR surface strength at 20 times is called the surface strength F. However, if the fracture origin of the glass is separated by 2 mm or more from the load point of the sphere, it is excluded from the data for the average value calculation.

The method according to claim 1,
Wherein the glass is an aluminosilicate glass, an aluminoborosilicate glass, or a soda lime glass.

3. The method according to claim 1 or 2,
The chemical strengthening glass according to the relational expression (I), wherein the range of a is -0.240 to -0.030 and the range of b is 0.020 to 0.215.

3. The method according to claim 1 or 2,
The chemical strengthening glass according to the relationship (I), wherein the range of a is -0.210 to -0.050 and the range of b is 0.030 to 0.210.

3. The method according to claim 1 or 2,
And an average hydrogen concentration c in the region of depth X = 0.1 to 0.4 탆 from the outermost surface of the glass is 0.070 to 0.150 mol / L.

3. The method according to claim 1 or 2,
Wherein the surface strength F is F > = 1800 x t ² with respect to the thickness t of the glass plate, the unit of the surface strength F is N, and the unit of the plate thickness t is mm.

3. The method according to claim 1 or 2,
Mol%, SiO ₂ in an amount of 50 to 80%, Al ₂ O ₃ 2 to 25%, Li ₂ O 0 to 10%, Na ₂ O 0 to 18%, K ₂ O 0 to 10%, MgO 0 to 15%, CaO 0 to 5% and ZrO ₂ to 0 To 5%.

3. The method according to claim 1 or 2,
With a composition represented by mol%, 50 to 74%, Al ₂ O ₃ from 1 to 10%, to 14% of Na ₂ O, 3 to 11% of K ₂ O, the MgO 2 to 15% of SiO ₂ 0 to 6% of CaO and 0 to 5% of ZrO ₂ , the total content of SiO ₂ and Al ₂ O ₃ is 75% or less, the total content of Na ₂ O and K ₂ O is 12 to 25% , The sum of the contents of MgO and CaO being 7 to 15%.

3. The method according to claim 1 or 2,
With a composition represented by mol%, 68 to 80%, Al ₂ O ₃ 4 to 10%, 5 to 15% of Na ₂ O, of K ₂ O 0 to 1%, the MgO from 4 to 15% of SiO ₂ and the chemical strengthened glass containing ZrO ₂ 0 to 1%.

3. The method according to claim 1 or 2,
With a composition represented by mol%, 67 to 75% of SiO _2, Al ₂ O ₃ 0 to 4%, 7 to 15% of Na ₂ O, of K ₂ O 1 to 9%, the MgO 6 to 14% And 0 to 1.5% of ZrO ₂ , the total content of SiO ₂ and Al ₂ O ₃ is 71 to 75%, the total content of Na ₂ O and K ₂ O is 12 to 20%, and the content of CaO Chemical content of less than 1%.